Inkjet cartridges are now well known in the art and generally comprise a body containing an ink supply and having electrically conductive interconnect pads thereon and a printhead for ejecting ink through numerous nozzles in a printhead. In thermally activated inkjet cartridges, each cartridge has heater circuits and resistors which are energised via electrical signals sent through the interconnect pads on the cartridge. Each inkjet printer can have a plurality, often four, of cartridges each one having a different colour ink supply for example black, magenta, cyan and yellow, removably mounted in a printer carriage which scans backwards and forwards across a print medium, for example paper, in successive swaths. When the printer carriage correctly positions one of the cartridges over a given location on the print medium, a jet of ink is ejected from a nozzle to provide a pixel of ink at a precisely defined location. The mosaic of pixels thus created provides a desired composite image.
Inkjet cartridges are increasingly becoming more sophisticated and complex in their construction and longer lifetimes are also required of cartridges, particularly those for use with printers having an off-carriage ink reservoir which replenishes the cartridge's ink supply. This has lead to greater sophistication in the so-called "servicing" of cartridges by a printer. It is normal for printers to have a service station at which various functions are performed on the cartridges while they are mounted in the printer carriage such as wiping, spitting and capping, see for example U.S. Pat. No. 5,585,826. Wiping comprises moving a wiper of a specified material across the printhead of a cartridge to remove paper dust, ink spray and the like from the nozzle plate of the printhead. Spitting, ejecting ink into a spittoon in the service station, is performed to prevent ink in nozzles which have not been fired for some time from drying and crusting. Cartridges are capped by precisely moving the printer carriage, and normally the cap too, within the service station, so that the cap mates with the printhead of the cartridge and forms a seal around the nozzle plate. Capping prevents ink on the printhead and in the nozzles from drying by providing the correct atmosphere around these components and thus reduces the risk of crusting and ink plug formation in the nozzles. Also the cartridge can often be primed while in the capped position by the application of a vacuum through the cap.
All of these servicing functions require that the cartridges held in the printer carriage are accurately located within the service station area of the printer relative to the servicing components. There are various prior art means known for mechanically aligning the printer carriage with service components such as caps, wipers and spittoons. For example, U.S. Pat. No. 5,563,638 by Osbourne entitled INK-JET PRINTHEAD CAPPING AND WIPING METHOD AND APPARATUS describes a sled on which is mounted a plurality of caps and wipers. The sled is cam-coupled to the printer chassis and also to the printer carriage so that movement of the printer carriage along its scanning axis produces relative movement and alignment between the cartridges held in the printer carriage and the servicing components held on the sled. As the servicing functions required within an inkjet printer become more sophisticated there is a requirement for greater accuracy in the alignment of cartridge printheads with the servicing components. Also, to facilitate a greater degree of flexibility in the design of service components there is a requirement that their alignment to the printer carriage is achieved other than by the movement of these components by the printer carriage. This is an especial requirement when the servicing components are intended to be manually removable by a user of the printer.